Factors Affecting Side Effects, Seroconversion Rates and Antibody Response After Inactivated SARS-CoV-2 Vaccination in Healthcare Workers

Abstract

In this study, it was aimed to prospectively evaluate the efficacy, side effects and seroconversion data of inactive severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), CoronaVac (R) (Sinovac, China) vaccine in healthcare workers. A total of 1053 healthcare workers who were initially seronegative (COV2T (R) SARS-CoV-2 Total Siemens, USA) and vaccinated with inactivated SARS-CoV-2 were included in the study. Quantitative IgG antibodies (ADVIA Centaur (R) SARS-CoV-2 IgG, Siemens, USA) were investigated 28 days after the first vaccine (n=939) and the second vaccine (n=771). In addition, neutralizing antibodies were evaluated via "enzyme linked immunosorbent assay (ELISA)" test (ACE2-RBD Neutralization Assay, Dia-Pro, Italy) 28 days after the first vaccine. Antibody response of the vaccine was evaluated statistically by univariate (Chi-square, Fisher's exact test, Student's t test, Mann-Whitney U, one-way ANOVA and Kruskall Wallis ANOVA tests) analysis and linear regression models. The consistency between quantitative IgG test and neutralizing antibody test was also evaluated in blood samples taken 28 days after second vaccination. Statistical analysis was determined in logarithmically transformed data with statistical analysis with SPSS 23.0 and Stata, and type 1 error level was accepted as 0.05. At least one side effect was reported by 31.3% and 26.8% of the participants after the first and second vaccine, respectively. The most frequent side effect was pain at the injection site with a frequency of 20.4% vs 21.7%. The frequency of applying to a health center due to side effects was 1.0% after the first vaccine and 0.8% after the second vaccine. The percentage of those who produced sufficient quantitative IgG was found as 25.3% (95% CI=22.5-28.1) 28 days after the first vaccine and 97.9% (95% CI=96.9198.93) after the second vaccine. Neutralizing test antibody positivity was found as 97.7% 28 days after the second vaccine. In univariate analysis, the characteristics that significantly increased the quantitative IgG response against inactivated SARS-CoV-2 vaccine were young age (p<0.01), female gender (p< 0.01), being a non-smoker (p<0.001), not having a chronic disease (p=0.019), having had the flu vaccine this year (p=0.012), not being overweight or obese (p=0.020), and having a SARS-CoV2 infection prior to vaccination (p<0.001). In addition, allied health personnel showed significantly lower antibody responses than the other workers (p<0.001). Multiple linear regression models revealed that, female gender, younger age, smoking and previous COVID-19 polymerase chain reaction test positivity significantly affected the quantitative IgG response after vaccination. A 99% agreement was found between the ELISA-based neutralizing antibody test and the quantitative IgG test (Kappa p=0.783) performed on the 28th day after the second vaccination. CoronaVac (R) provides adequate antibody response in 25% of healthcare workers aged 18-64, after 28 days from a single vaccine, and 97% after 28 days from the second vaccine. Antibody response was significantly higher in younger ages, women, non-smokers, and those who had previously encountered SARS-CoV-2. Phase 3 and phase 4 results are needed to show effectiveness of this vaccine in real life.